The title says it all. It took 20 minutes to sync a screenshot on Android. And there is no way to “force sync!” Is it caused by recent Google permission revoke? I don’t think so.
NextCloud is great! But this sync behavior is frustrating. And I believe it is so easy to fix, probably a dozen lines of code.
I can not really help you. But maybe you can find your issue at nextcloud/android issues. Do you have a Github account? If not, find the issue, give us more details and we can add your information to the issue on Github.
One interesting observation I made is: If I install nextcloud and choose pretty much the default folders, then everything uploads and synchronised quickly. But when I changed later some folders and setting the way I wanted it, synchronisation takes longer. Much longer. In my case around half hour. It doesn’t bother me in the least thought. Even if it is once a day is still OK for my data backup purposes 